One conventional controlled damper assembly includes a piston attached to a hollow piston rod containing two insulated wires. The piston slides within a damper cylinder filled with a damping fluid to dampen motion between a first member attached to the damper cylinder and a second member attached to the rod end which extends from the damper cylinder. One example of a controlled damper assembly is a magnetorheological (MR) damper assembly having a coil (also called an MR coil) in the piston to change the damping characteristics of an MR damping fluid wherein the two insulated wires connect to respective ends of the coil. Another example of a controlled damper assembly is a solenoid-valve damper assembly. The use of two insulated wires creates problems with packaging, cost, and complexity in design and manufacturing process.
Another conventional controlled damper assembly uses one insulated wire connected to one end of the MR coil (or one terminal of the solenoid valve) and has the other end of the coil electrically connected to the piston rod (or the other terminal of the solenoid valve). One side of an electrical connector makes separate connection with the insulated wire and the rod end. The other side of the electrical connector has insulated wire leads connected to a vehicle electronic control unit (ECU). However, in a strut application, the piston rod is electrically connected to the strut housing creating an alternative electrical return path through the vehicle ground. The use of the vehicle ground in providing an electrical return path creates problems with the electronic control unit (ECU). In particular, because other electrical components may also utilize the common secondary path, the vehicle ECU may be unable to independently track the status of the piston and damper assembly of the vehicle. For example, this arrangement prevents the ability to detect the loss of the damper electrical return path to the ECU via the harness electrical connection to the ECU. In addition, if there is a short in the system (i.e. a short from the vehicle battery), the electrical short may travel through the damper assembly and adversely affect its performance.
What is needed is an improved controlled damper assembly.